The present invention relates to an adjustable chair construction having an adjustable back, seat, and armrests configured to provide optimal postural support to a seated user during recline. More particularly, the back includes a flexible back shell and a lumbar mechanism for adjusting a shape of the flexible back shell for improved lumbar support. The chair further includes a seat, a reclineable back, and (in one version) armrests that move with a synchronous motion relative to the seat and back during recline of the back.
There are many adjustable chairs in the art, including chairs having adjustable backs and adjustable armrests. However, adjustability continues to be a concern since users have so many different body shapes and preferences. Further, improvements are desired in the adjustment mechanisms, so that they are simpler and more intuitive to operate.
In regard to synchronized seat and back movements, synchronous chairs, such as Steelcase""s Sensor chair, have gained wide market acceptance for providing postural support during back recline while also providing simultaneous seat and back rotation that minimizes sheer or xe2x80x9cshirt pullxe2x80x9d in the lumbar area of a seated user. However, further improvement is desired so that these mechanisms provide even greater adjustability in terms of the particular synchrotilt motion that they provide. For example, a non-uniform synchronous motion is often desired, where the back and seat move at a changing ratio during recline. From a manufacturing standpoint, it is preferable that these new movements and back tilt axis locations still use as many existing parts as possible, and that they be as simple as possible. Also, many consumers are looking for a new modernistic appearance.
In regard to armrests, there are many adjustable armrests on the market, some of which move with the seat during recline of the back and others of which move with the back during recline. However, no known existing chair includes adjustable armrests that move with a synchronous rotating motion during back recline that is different from both the back and the seat. Further, no known chair includes means for adjusting an armrest in a manner that causes the synchronous angular rotation of the armrest and its rotational path to change depending upon the adjustment. Also, an adjustable armrest is desired that is horizontally rotatable to different angular/lateral positions, yet that is secure and also intuitive to operate and adjust. At the same time, these motions preferably are provided by an adjustment mechanism and armrest support structure that is cost effective, readily manufacturable, and that provides a modernistic and pleasing visual appearance.
Accordingly, a chair including an improved back construction, armrest construction, and overall construction is desired solving the aforementioned problems, but that provides the adjustability, low cost, and ease of assembly needed in the competitive chair industry.
In one aspect of the present invention, a seating unit includes a base having a control assembly, a seat assembly pivoted to the control assembly for movement about a seat tilt axis, and a back assembly pivoted to the control assembly for movement about a back tilt axis. The back assembly includes a back support structure and a flexible sheet includes an upper portion attached to and supported by the back support structure. The flexible sheet also includes a lower portion coupled to the back support structure for holding the lower portion rearwardly. A vertically-adjustable lumbar mechanism is adjustably supported on the back support structure and operably engages the flexible sheet for biasing an intermediate portion of the flexible sheet forwardly to both form the intermediate portion into a forwardly convex shape for postural lumbar support and also to tension the flexible sheet between the upper, intermediate, and lower portions.
In another aspect of the present invention, a seating unit includes a base having a control assembly, a seat assembly pivoted to the control assembly for movement about a seat tilt axis, and a back assembly pivoted to and supported by the control assembly for movement about a back tilt axis. The back assembly includes a back support structure and a flexible sheet. The back support structure includes corner frame members attached to and supporting upper outer corners of the flexible sheet with the flexible sheet hanging downwardly therefrom. A vertically-adjustable lumbar mechanism is mounted to the back support structure and operably engages a lower portion of the flexible sheet in a manner that adjustably spaces the flexible sheet forwardly away from the back support structure in an intermediate portion of the flexible sheet for providing lumbar support to a seated person.
In still another aspect of the present invention, a seating unit includes a base having a control assembly, a seat assembly pivoted to the control assembly at a fixed seat tilt axis and being movable between a seat upright position and a seat recline position, and a back assembly pivoted to the control assembly at a fixed back tilt axis and being movable between a back upright position and a back recline position. The control assembly is configured to, during recline, cause at least a portion of the seat assembly to pivot and raise as the seat assembly is moved from the seat upright position toward the seat recline position.